Graphene is a planar sheet of carbon atoms arranged in honeycomb lattice, which has attracted attention owing to its extremely high mobility, thermal conductivity, and strongly tunable electrical conduction, which can be controlled with the gate bias. Device applications of graphene for high frequency, analog, mixed signal communication and THz generation have been proposed. For example, graphene chemical vapor deposition (CVD) growth and other synthesis techniques together with development of the large-scale quality control methods for graphene can make practical applications of graphene feasible.
Graphene, with its extremely high surface-to-volume ratio, can become a natural choice material for sensor applications. The single-molecule sensitivity of graphene devices has been demonstrated at the early stages of graphene research. For example, it has been suggested that the exceptional surface-to-volume ratio, high electrical conductivity, low thermal and 1/f noise, relatively low contact resistance, and ability to strongly tune the conductivity by the gate in graphene transistors may make them promising for gas sensing applications. Graphene resistivity, frequency of the surface acoustic waves (SAW), Hall resistivity, and the shift of the Dirac voltage has been used as sensing parameters. For example, the sensitivity of graphene devices to NH3, NO2, CO, CO2, O2, has been demonstrated. The high-gas sensitivity of graphene, which leads to its ability to detect ultra-low concentrations (down to less than 1 ppb) of different gases, and the linear dependence of the response to the gas concentration have been disclosed in several publication.
However, the selectivity of the graphene-based gas sensors is much less explored for the sensors utilizing all the above-mentioned sensing parameters. In accordance with an exemplary embodiment, the low-frequency noise can be used as the sensing parameter to enhance selectivity is demonstrated. For example, while the electrical resistivity or other DC parameter can serve as a quantitative parameter to measure the gas concentration, the low-frequency noise can help to discriminate between individual gases.